This invention relates to aluminum and more particularly it relates to an anode for use in the electrolytic production of aluminum from alumina dissolved in a molten salt electrolyte.
The use of low temperature electrolytic cells for producing aluminum from alumina has great appeal because the cells are less corrosive to materials comprising the cell. Inert anodes have exclusively been suggested for use in the low temperature cells. However, the use of inert anodes has the problem that the inert anodes require a decomposition voltage for alumina of about 2.3 to 2.6 volts. This adds greatly to the cost of electricity required to produce aluminum from alumina. Thus, it would be advantageous to produce aluminum in a low temperature, electrolytic cell having a lower decomposition voltage.
Different shaped anodes have been suggested in the various electrolytic processes. For example, U.S. Pat. No. 4,457,813 discloses electrolytic reactions carried out simultaneously at the anode and cathode of a diaphragmless electrolytic cell. This cell contained a three dimensional porous platinum-plated graphite anode (5xc3x971xc3x970.5 cm.) embedded centrally in one wall of a polypropylene cell body (61xc3x9715xc3x972.5 cm.) In this process, separate useful reactions are conducted at an anode and cathode, respectively, by electrolysis of an anolyte at an anode and a catholyte at the cathode wherein the anolyte and catholyte are of different composition and are prevented from contacting the cathode and anode, respectively, during electrolysis without the use of selective permeable membranes or permeable partitions.
U.S. Pat. No. 4,568,439 discloses an electrolytic cell which has a spacing means positioned between the anode and cathode faces. The present spacing means comprises a plurality of longitudinally elongated, electrically non-conductive spacers fabricated of a chemically resistant material being inert to the conditions existing within an operating electrolytic cell. The present spacers are positioned on the face portion of a foraminous anode. The spacers are secured on the anode face by extension of a portion of the spacer through an opening in the anode and are secured at the back portion of the anode.
U.S. Pat. No. 4,670,113 discloses a process for the gasification or combined gasification and liquefaction of carbon or carbonaceous materials by utilizing electrochemically generated atomic hydrogen to activate the chemical reaction between the ions of dissociated water and the carbon or carbonaceous material in an electrolysis cell, thereby producing gaseous or combined gaseous and liquid products in amounts exceeding the Faraday equivalents of such products for the amount of electrical energy consumed.
U.S. Pat. No. 4,938,853 discloses non-adherent copper metal particles (xe2x80x9cfinesxe2x80x9d) formed in a plating bath during the course of autocatalytic electroless copper deposition onto activated substrate surfaces are oxidized and redissolved in the bath by brief application of current between an anode element and a cathode element immersed in the bath, the anode element being comprised of an anode surface substantially parallel and proximate to the bottom surface of the vessel containing the bath.
U.S. Pat. No. 5,908,715 discloses a composite particulate material for use in anodes of lithium-ion batteries. The particles of the material include a graphite core that has been provided with a surface layer including a non-graphitizable carbonaceous material. The graphite core has an interplanar spacing of at least about 0.346 nm. The method of producing the composite is also disclosed.
From the above, it will be seen that there is a need for a low temperature electrolytic cell capable of producing aluminum at a low decomposition voltage to reduce the cost of electricity required for producing aluminum in such cell.
It is an object of the present invention to provide an improved method for producing aluminum from alumina in an electrolytic cell.
It is an object of the invention to provide an improved method for producing aluminum in a low temperature electrolytic cell.
It is still another object of the invention to provide an improved method for supplying alumina-enriched electrolyte to the active surface of an improved anode in a low temperature electrolytic cell for producing aluminum.
And, it is another object of the present invention to provide a method of operating a low temperature electrolytic cell employing planar carbon anodes for producing aluminum from alumina.
These and other objects will become apparent from the specification, claims and drawings appended hereto.
In accordance with these objects, there is provided a method of producing aluminum in an electrolytic cell containing alumina dissolved in an electrolyte, the method comprising providing a molten salt electrolyte at a temperature of less than 900xc2x0 C. having alumina dissolved therein in an electrolytic cell. A plurality of anodes and cathodes having planar surfaces are disposed in a generally vertical orientation in the electrolyte, the anodes and cathodes arranged in alternating or interleaving relationship to provide anode planar surfaces disposed opposite cathode planar surfaces, the anode comprised of carbon. Electric current is passed through anodes and through the electrolyte to the cathodes depositing aluminum at the cathodes and forming carbon containing gas at the anodes.